1. Field of the Invention
The invention relates to a system for the stereoscopic reproduction of images, such as video clips, films, etc.
2. Description of the Background Art
There are various techniques for three-dimensional reproduction. The anaglyph technique has been long known: A stereoscopic impression forms for the viewer by simple red/green superimposition of both left/right partial images and viewing of the total image through filter glasses, which let through only the corresponding color component for a particular eye. A drawback here is the system-related color filtering, so that no realistic color images can be reproduced with this technique.
Another method, occasionally used in television, is the Pulfrich method. Here as well, glasses are used for viewing, whereby the light beam for one eye is darkened more greatly than for the other, however. For this purpose, color glasses are also frequently used (for reasons of cost), although it is only a question of the different darkening. Because of the different brightness, the visual information reaches the processing areas of the brain with a slight delay. If a shown scene moves at a right angle to the viewer, parallax therefore results for an eye because of the time delay in the perception and the scene is perceived spatially. The advantage of this technique is the simplicity of the reproduction technique. It is disadvantageous that the scene must be in constant motion, which is often perceived as unpleasant after a certain time period. In addition, the scene must always move in the same direction, because otherwise the depth information would reverse. The motion speed must also be kept constant, because otherwise the depth information cannot be rendered correctly.
In the computer field, a different method is often used: The right/left components in this regard are separated by so-called shutter glasses, which by means of electrically switchable polarization filters let light through, e.g., from a monitor or projector, alternately only for the viewer's right or left eye. The shutter glasses in this regard are synchronized with the display device (e.g., a monitor), so that of the alternating sequence, shown there, of left/right partial images accordingly only the specific partial images reach the left or right eye. This technique in fact offers a true-color reproduction but does have the drawback that the brightness is greatly reduced, because (alternately) the image reproduction is perceived only by one eye of the viewer (therefore only half of the total brightness of the monitor) and in addition the polarization filters on their own already absorb light (in the transmission phase as well). In addition, the constant left/right fade-out requires a very high refresh rate (at least 120-160 Hz) so that an interfering flicker effect is suppressed.
Another principle is based on interference filter technology. A method for generating an image reproduction, perceptible optically three-dimensionally, according to the interference filter technology or a corresponding stereoprojection system is known from DE 199 24 167 B4, which corresponds to U.S. Pat. No. 6,698,890. In this regard, two interference filters with a slightly different spectral filter effect are used for projection. The passbands of both filters in this regard are arranged shifted relative to one another such that they have no overlap and are therefore formed orthogonal to one another. With the use of both interference filters, which are orthogonal to one another and which, in each case, have three passbands for the three primary valences in the range of blue, green, and red color perception, two separate images, one for the left eye and one for the right eye, can be realized with the help of which a three-dimensionally perceptible image can be projected onto a screen. This image is perceived by a viewer selectively by the separate eyes in that he has a pair of glasses whose left lens has a filter characteristic according to the one interference filter and the right lens a filter characteristic according to the other interference filter. As a result, both images can be reliably separated from one another in an eye-specific manner on the screen and create the stereo effect or the three-dimensional effect of the images in the viewer. The term wavelength-division multiplexing method is also used.